Utility lines for water, electricity, gas, telephone, and cable television are often run underground for reasons of safety and aesthetics. Horizontal directional drilling (HDD) is often used for placement of such utility lines. In a typical horizontal directional drilling sequence, the horizontal directional drilling machine drills a hole into the ground at an oblique angle and then drives a series of interconnected drill rods (i.e., a drill string) along a substantially horizontal path to create a horizontal hole. It is common to attach a utility line or other conduit to the drill string so that it is dragged back through the hole.
A typical horizontal directional drilling machine includes a frame on which is mounted a drive mechanism that can be slidably moved along the longitudinal axis of the frame. The drive mechanism is adapted to rotate the drill string about its longitudinal axis. Sliding movement of the drive mechanism along the frame, in concert with the rotation of the drill string, causes the drill string to be longitudinally advanced into or withdrawn from the ground.
A horizontal directional drilling machine also includes a rod box (i.e., a rack or magazine) for storing rods (i.e., pipes or other elongated members) used to make the drill strings. The more drill rods that are stored on the horizontal directional drilling machine, the longer the horizontal directional drilling machine can operate continuously. Further, storing drill rods on the horizontal directional drilling machine makes transportation and operation of the machine more efficient.
However, horizontal directional drilling machines are constrained by certain size requirements, and, therefore, the size of the rod box on the horizontal directional drilling machine is also constrained to certain size requirements. For example, the height of the horizontal directional drilling machine can be limited based on the location of the machine's center of gravity so as to prevent instability of the machine. Further, the width of the rod box, and the horizontal directional drilling machine in general, is also important as the horizontal directional drilling machine will need to be moved (i.e., driven) to the worksite from a trailer. Therefore, the ability to fit through certain narrow openings, such as gates, is important to the usefulness of the horizontal directional drilling machine.
Therefore, improvements are needed to increase or at least maintain (e.g., relative to a standard rod box) the capacity of rod boxes while also maintaining certain horizontal directional drilling machine dimensions.